(a) Technical Field
The present disclosure relates to a molding apparatus for a rotor of a motor, and more particularly to a molding apparatus for fixing a magnet in a rotor core of a permanent magnet synchronous motor.
(b) Background Art
In general, a driving motor as a power source is used in environmental vehicles such as hybrid electric vehicles or electric vehicles. Like a general motor, the driving motor includes a stator in which a coil is wound on a stator coil, and a rotor disposed within the stator and in which a permanent magnet is inserted into a rotor core.
In general, in order to fix a permanent magnet to the rotor core, a method of applying a bond to a permanent magnet insertion hole of a rotor core, inserting a permanent magnet into the permanent magnet insertion hole, and curing the bond, or an insert insertion method of injecting a resin in a permanent insertion hole of a rotor core into which a permanent magnet is inserted and curing the resin is mainly used.
For example, a method of disposing a rotor core into which a permanent magnet is inserted within an upper mold and a lower mold, injecting a resin into a space in a permanent insertion hole in which the permanent magnet is positioned, and fixing the permanent magnet is mainly used. However, the insertion injection molding requires the following premises. That is, when the size and the shape tolerance of a product are smaller than those of a mold, the product should be able to move in the mold. In contrast, when a precise insert injection molding process is necessary, a product should be fixed and the size and shape tolerance of the product should be those of the mold or more. Otherwise, a flash is essentially generated in the injection molding process.
When a high speed/high torque/high durability condition is required as in a rotor of a driving motor for environmental vehicles, the latter condition should be satisfied for a precise molding performance. However, the flatness and parallelism of a rotor core made by stacking thin plates are lower than those of a precise product due to incomplete attachment of the thin plates caused by embossing for a thickness deviation of a thin plate of the core and stacking of the thin plates. Accordingly, flashes may be frequently generated in theory.
In the rotor core, the plates are assembled through embossing in a progressive mold and then the product is extracted. The coupling is progressed by a press in a mold, and the thickness of the rotor core is measured while being pressed. However, after the product is extracted, the core is swollen again by incomplete adhesion of the thin plates due to embossing (spring back). When the mold is closed, the stack thickness of the core having the characteristics is larger than a distance between the upper and lower plates. When the mold is closed, the thickness of the core is reduced, and in this process, the uppermost plate and the lowermost sheet have an improved precision by the precise and strong mold. Further, the intermediate core plates are deformed to a natural state as in a soft material.
A stack core which does not satisfy the premises of a general insert injection molding process may be molded through the mechanism. However, in recent years, a method of stacking a core employs a coupling method not using embossing but using a bond. Accordingly, a spring back phenomenon is reduced as compared with a embossed core, so that flashes are frequently generated.